Search results

Title: PROCESSING OF IRON BASED OXIDE DISPERSION STRENGTHENED ALLOYS
Creator: Siddhanthi, Rohan Ashok
Date: 2011-12-19, 2011-12
Description: In this research the Oxide Dispersion Strengthened (ODS) Steel alloy 14 YWT with composition Fe- 14 Cr – 3 W – 0.4 Ti – 0.25 Y2O3 was...
Show moreIn this research the Oxide Dispersion Strengthened (ODS) Steel alloy 14 YWT with composition Fe- 14 Cr – 3 W – 0.4 Ti – 0.25 Y2O3 was consolidated using liquid phase sintering method and it’s mechanical properties were tested and compared with standard materials. Initially the standard composition was prepared by mechanical alloying and cold compacted in to compression samples and then sintered. The consolidated sample density was determined and their compression tests were performed at various temperatures. To improve the strength aluminum powder was added into the mechanically alloyed samples via milling for 15 minutes with the aim to enhance diffusion by liquefying at higher temperatures. Initially specimens with different weight percentage of aluminum were prepared and it was discovered that 2.5% aluminum addition gave the best results; further testing was carried out at this alloy composition. The tests were carried out for 2 different post sintering processes. Tests were also carried out with copper as the sintering agent. A significant increase in yield strength with the addition of 2.5% Al and 10% cold working was observed.
M.S. in Material Science, December 2011
Show less

Title: Rotary kiln
Creator: Soper, E.
Date: 2009, 1910
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/rotarykiln00sope
Thesis (B.S.)--Armour Institute of Technology

Title: Resilience tests of automobile tires under commercial conditions of operation
Creator: Vanderkieft, Nicholas, Yorke, William H
Date: 2009, 1913
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/resiliencetestso00vand
Thesis (B.S.)--Armour Institute of Technology

Title: The representation of automobile engine economy performance by surfaces
Creator: Anderson, H. G., Keeth, J. A
Date: 2009, 1919
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/representationof00ande
Thesis (B.S.)--Armour Institute of Technology, 1919 B.S. in Mechanical Engineering, 1919

Title: The representation of automobile engine characteristics by surfaces
Creator: Cook, Ellis N., Gail, Arthur N
Date: 2009, 1920
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/representationof00cook
Thesis (B.S.)--Armour Institute of Technology

Title: Shock absorption of automobile tires
Creator: Marvin, Norton L., Jackson, Maurice M
Date: 2009, 1920
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/shockabsorptiono00marv
Thesis (B.S.)--Armour Institute of Technology

Title: Computational Techniques for Wind Turbine Power Prediction
Creator: Goyal, Udit
Date: 2011-11-28, 2011-12
Description: Wind energy is expected to play an important role in meeting the ever- increasing energy requirements and reducing our dependence on...
Show moreWind energy is expected to play an important role in meeting the ever- increasing energy requirements and reducing our dependence on conventional sources of energy. Wind turbines are broadly classfied as horizontal-axis and vertical-axis depending upon the orientation of the rotor shaft relative to the wind direction. Considerable research has been carried out on horizontal-axis wind turbines, which today are sophisticated and efficient electro-mechanical systems. Continuous research and development in areas of electronics, controls and instrumentation aids in the advancements of this technology. From an aerodynamic point of view the Betz limit is known to impose theoretical limit on the power extraction of propellers. The momentum balance equations show that the maximum of 59.3 percent of free-stream energy can be extracted by propellers. This limit, however is not well de fined, particularly when considering diff user and nozzle-augmented wind turbines with local flow accelerations. In this study the actuator disk approach is used to model the momentum loss across a wind turbine rotor and simulate the Betz limit using Fluent software. This approach is subsequently applied to study the coefficient of performance expected from dif user and nozzle-augmented wind turbines. Vertical-axis wind turbines, on the other hand, are still not completely understood in terms of blade aerodynamics and are the focus of various research studies. Large variations in angle of attack and wake evolution downstream of the blade have a time-dependent e ffect on the blade forces, instantaneous torque and hence the coefficient of power of the turbine. Since Navier-Stokes solutions for vertical- axis wind turbines are expensive and complicated, various low-cost models have been developed based on momentum balance such as single, double and double multiple- streamtube formulations. These models, however, use static lift and drag data for the airfoils as inputs, neglecting the unsteady e ffects on aerodynamic coefficients. In the present study, an alternative approach based on the panel method is explored further for developing a low-cost computational method for simulating the aerodynamics of vertical-axis wind turbines. At each time step an airfoil is represented as a combination of source and vortex distributions which induce a potential in the flow fi eld. A time-stepping mechanism is implemented satisfying the Kutta and the Kelvin Helmholtz condition for the wake evolution behind the rotating blades. The e ffect of this vortex evolution on the aerodynamic forces on the airfoil is studied, focusing on the coefficient of performance (Cp) of the blade. Results show a decrease in Cp values till the wake attains a quasi steady state. A comparison study is performed with other computational models, showing the importance of the wake evolution in time. An optimization of the blade pitch angle is also performed by defi ning a composite variable pitch function in order to improve the torque and hence the instantaneous power from the blades.
M.S. in Mechanical and Aerospace Engineering, December 2011
Show less

Title: DESIGN AND FABRICATION OF AN UNMANNED GROUND VEHICLE UTILIZING VARIABLE INTERNAL INERTIAL PROPERTIES
Creator: Ruffatto Iii, Donald
Date: 2011-11-27, 2011-12
Description: Mobility of an Unmanned Ground Vehicle (UGV) is highly dependent upon the maximum lateral and longitudinal forces that can be generated at the...
Show moreMobility of an Unmanned Ground Vehicle (UGV) is highly dependent upon the maximum lateral and longitudinal forces that can be generated at the tire/ground interface. These forces are a function of a number of di erent vehicle properties such as suspension geometry, actuators and the tire/terrain interaction mechanics. Typically these properties are xed imposing general limits to the vehicle's maximum achievable lateral and longitudinal accelerations. If you were instead able to modify these parameters dynamically during vehicle operation substantial improvements in robot mobility can be realized. This thesis presents the design a fabrication of the Variable Inertial Vehicle (VIV) which is capable of realizing this. It uses a shifting mass mechanism to vary the normal load distribution among the front and rear tire based upon the desired operating conditions. The shifting mass mechanism is capable of moving a substantial amount of the vehicle along it longitudinally. This provides direction control of the tire normal forces during operation. Described in this thesis is the design of this unique element and its e ects on the rest of the vehicle design. The other main elements di erentiating the VIV from common UGV's such as the electronics, suspension, chassis, and powertrain are also detailed. Finally, a number of experiments utilizing the VIV are presented. These experiments were devised and performed my Chenghui Nie but are presented here to demonstrate the functionality and capabilities of the VIV.
M.S. in Mechanical Engineering, December 2011
Show less

Title: Power developed by an hydraulic ram
Creator: Brock, W. L., Scott, P. J.
Date: 2009, 1906
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/powerdevelopedby00broc
Thesis (B.S.)--Armour Institute of Technology

Title: THE EFFECT OF RUTHENIUM ADDITION ON THE PHASE EQUILIBRIA, MECHANICAL PROPERTIES AND OXIDATION RESISTANCE OF TIAL-BASED ALLOYS
Creator: Liu, Qizheng
Date: 2012-05-11, 2011-12
Description: The high temperature phase equilibria in the Ti-Al-Ru ternary system have been investigated but there remain some ambiguous regions. In this...
Show moreThe high temperature phase equilibria in the Ti-Al-Ru ternary system have been investigated but there remain some ambiguous regions. In this work arc-melted alloys were studied using scanning electron microscopy, X-ray diffraction and optical microscopy to determine the isothermal section of Ti-Al-Ru system at 1200°C. The lattice parameters were calculated from X-ray diffraction pattern for some compounds, including LI, 8-Ruso(TixAlso-x) and (AI6o-xTix)Ru4o. The lattice parameter of these three phases generally increases with Ti content. Enthalpy of formation was also measured for LI and 8-Ruso(TixAlso_x) with direct synthesis calorimeter to compare with the lattice parameter change. The enthalpy of formation of LI matches its lattice parameter change, but 8-Ruso(TixAlso_x) shows a reversed trend. It suggests that addition of Ti introduces a stronger bonding in the 8-B2 phase super-lattice. The phase equilibria are discussed in comparison with published research work. A new three phase region was detected for L t, Y and Til_xAl 1+x by X-ray diffraction. The homogeneity region of (AI6o-xTix)RU4o was found to be much higher than previously reported, with almost constant Ru content. The results from the ternary isothermal section also help to clarify the uncertain parts of the binary Ti-Al phase diagram. Three ternary eutectic reaction temperatures were measured with differential scanning calorimetry and the results were compared with the published liquidus projection. The high temperature compression behavior of TiAl-Ru alloys was studied at different temperatures and strain rates. Ru was found to have a strong strengthening effect on TiAI alloys. However the Ru addition amount was limited by its low solubility in y-TiAI and U2-Ti3AI, and the detrimental effect of excessive ternary phase precipitation. Furthermore, the melting temperature decreases when Ru 2:0.6at% as the alloy composition approaches a ternary eutectic point. The strengthening mechanism is discussed and two separate mechanisms are proposed, viz. solid solution strengthening and refined colony strengthening. Intergranular cracks were found in the alloys with low Ru or no Ru addition, but were barely detected as Ru content increased to above 0.6 at.%. It was suggested that Ru showed a beneficial effect on both strength and ductility of TiAI alloys due to the refined colony size. Three-point bend test results showed that the Ru addition can also improve the room temperature ductility of TiAl alloys. Hot workability was increased according to the compression tests. Thermal-mechanically treated TiAI-Ru had much smaller grain size than the heat-treated samples due to dynamic recrystallization. But it did not show superior strength in the compression test compared to the heat-treated samples. The Zener-Hollomon parameter was calculated from the compression strength of heat-treated TiAI-Ru alloys. Its relationship with dynamic recrystallization and hot work is discussed. The mechanical properties of TiAI-Ru alloys are compared with TiAI-Nb samples and demonstrate a promising combination of strength and ductility. The high-temperature oxidation resistance ofTiAI alloys with constant AI content and different alloying elements was tested with thermogravimetric calorimeter. Both Ru and Nb additions were found to have beneficial effect on the oxidation resistance ofTiAI alloys. While TiAI-Ru showed a slight improvement on the oxidation behavior, TiAI-Nb alloys had much better performance in comparison with TiAI alloys. Complicated oxide scale structure was characterized with the assistance of X-ray diffraction, scanning electron microscopy and Energy-dispersive X-ray spectroscopy analysis. The different oxide scale structure among the TiAl, TiAl-Ru and TiAl-Nb alloys were discussed with respect to their thickness, spatial pattern and composition gradient. The poor oxidation resistance of TiAI alloys at the testing temperature was determined to be attributed to the competition growth between Ah03 as well as Ti02, and the lack of a thick continuous Ah03 layer. The outward diffusion of Ti was found to be the controlling factor and the growth of Ti02 on top level of the oxide scale destroyed the initial Ah03 protection. RU02 was found to be the natural marker of the oxidation process in TiAl-Ru alloys due to its slow diffusion. The repartitioning of Ru in the oxide/substrate boundary was revealed to be the reason of its slight beneficial effect. Nb20 S layer was observed in the oxide scale of TiAl-Nb alloys and it played the role of blocking the outward diffusion of Ti. Thus Nb addition can suppress the growth of Ti02 and promote the formation of a continuous AI 20 3 layer. Treating the TiAI alloys by dipping in hydrofluoric (HF) acid was found to have a dramatic beneficial effect on TiAI alloys. Alloying elements have reversed effect on the HF dipping due to the reduced reaction rate with HF acid. The oxidation rate constant and activation energy were calculated for TiAI alloys with/without alloying addition. They were compared with the published data and the trend with composition change was discussed.
Ph.D. in Materials Science and Engineering, December 2011
Show less

Title: LOCALIZATION OF WIND TURBINE NOISE USING A COMPACT MICROPHONE ARRAY WITH ADVANCED BEAMFORMING ALGORITHMS
Creator: Ramachandran, Rakesh Chandran
Date: 2014, 2014-12
Description: The knowledge of noise source location on a wind turbine is crucial for de- signing low noise wind turbines. Even though there has been...
Show moreThe knowledge of noise source location on a wind turbine is crucial for de- signing low noise wind turbines. Even though there has been considerable e ort to theoretically predict the noise from wind turbines in the past, very few experimental investigations have been performed to validate these models. Currently, compliance standards for wind turbine noise are based on single microphone measurements at various designated locations around a wind turbine. This only provides amplitude and frequency data of the overall wind turbine noise. However, it is impossible to locate noise sources, and to understand the dominant noise generation mechanism, using single microphone measurements. A sophisticated method, namely, the use of a microphone phased array with beamforming is necessary to locate the noise sources. Even though microphone arrays have been widely used to study aircraft yover and jet noise, it has just recently found application in locating wind turbine noise. Typical microphone arrays that have been used in the past for monitoring aircraft noise and wind turbine noise are very large ranging up to 270 m2 in area with about 148 mi- crophones. The setup is xed for a particular wind turbine and takes a considerable amount of time. In this thesis it is shown that a compact microphone array (with 24 microphones spread over 1.5 m2) is su cient to locate and separate wind turbine noise sources successfully. It is also shown that in order to use a compact micro- phone array, advanced deconvolution based beamforming methods such as DAMAS, CLEAN-SC, LP, and TIDY are necessary. However, before attempting to validate our idea, it is necessary to understand the concept of array resolution and di erent methods to improve it. We start with an in-depth study on the microphone array resolution and the e ect of di erent beamforming algorithms on it. This study has resulted in several interesting results: (i) The resolution limits that govern the resolution of the imaging system in optics also govern the resolution of microphone array. (ii) The resolution is a function of source frequency, diameter of the array, separation distance between sources, and the distance between the array and the sources. (iii) The resolution lost due to the compact microphone array can be recovered by using deconvolution algorithms. (iv) Di erent algorithms are useful for di erent scenarios; CLEAN-SC is most e cient in extracting the dominant noise source from the source map, LP is e cient in locating multiple or extended noise sources, and TIDY is e cient in locating moving sources. (v) LP and DAMAS show superresolution. (vi) The dynamic range of source maps could be improved by eliminating the diagonal elements of CSM or CCM but care should be take as this could also eliminate weak sources. Following this study, we discuss the results from the full scale large wind tur- bine noise measurements. Our study focuses on the ability of a compact microphone array to successfully locate both mechanical and aerodynamic noise sources on the wind turbine. Several interesting results have emerged from this study: (i) A compact microphone array is su cient to perform a detailed study on wind turbine noise if advanced deconvolution methods are applied. (ii) Noise sources on the blade and on the nacelle can clearly be separated. (iii) Noise of the blades is dominated by trailing edge noise which is frequency dependent and is distributed along the length of the blade with the dominant noise source closer to the tip of the blade. (iv) The LP and DAMAS algorithms represent the distributed trailing edge noise source better than CLEAN-SC and conventional beamforming. (v) Additional tonal noise produced dur- ing yawing operation is believed to be radiating from the tower of the wind turbine that acts like a resonator. (vi) Ground re ection is not believed to have a signi cant e ect on noise source location estimates in this study. (vii) The asymmetry in the aerodynamic noise is attributed to the Doppler ampli cation e ect. Finally, the noise measurements made on the small scale wind turbine showed that the compact array was successfully able to separate out the mechanical and aerodynamic noise. The mechanical noise from the nacelle was found to be the dominant noise source below 3000 Hz and the aerodynamic noise from the blades was found to be dominant above 3000 Hz. The asymmetry in the aerodynamic noise was also present in this case. The study on mechanical noise found that gear box was the dominant noise source. It is hoped that the work presented in this thesis will serve as a guide to researchers who intend to use compact microphone arrays with advanced beamforming algorithms in the future and also to those who intend to validate theoretical models of wind turbine noise.
Ph.D. in Mechanical and Aerospace Engineering, December 2014
Show less

Title: MINIATURE SHOCK TUBE ACTUATORS FOR HIGH SPEED FLOW CONTROL APPLICATIONS
Creator: Ramachandran, Rakesh Chandran
Date: 2011-04-11, 2011-05
Description: In the field of aero-acoustics, one of the primary areas of interest has always been centered around the resonant flows. The fluid structure...
Show moreIn the field of aero-acoustics, one of the primary areas of interest has always been centered around the resonant flows. The fluid structure interactions gives rise to a reverberant field, which results in high amplitude fluctuating pressures associated with the resonant tones that could lead to sonic fatigue failure of sensitive components in the vicinity of such flows. One such fluid structure interaction is the cavity flow problem. Several flow control technologies exist to suppress cavity tones but most of them lose efficacy at off-design conditions and particularly at higher subsonic and supersonic flows. It is due to this fact that there is a high demand for high control authority flow control actuators. In order for an actuator to have higher control authority, one must be able to use a mechanism that has sufficient energy to disrupt the cavity tone generation mechanism at higher subsonic Mach numbers. One such mechanism is the shock tube generating high strength shock waves. To the best of our knowledge, there does not appear to be any use of shock waves to suppress noise emitted by cavity in aircrafts. The main challenge lied in developing the miniature shock tubes that could produce high intensity shock waves. In the present work, we designed, developed and tested these miniature shock tube flow control actuators. The initial part of this work involved a detailed study of the theory behind producing shock waves using a shock tube. The designing and development part included a lot of trial and error adjustments to produce shock waves as predicted by the 1D shock wave theory. Two shock tube actuators were developed, one having a single shock tube and another with three shock tubes but with the same exit area as the previous one. We carried out various characterization experiments measuring the unsteady pressure at the exit of these shock tubes and also the walls of the shock tube. The experimental investigation of the shock tubes revealed that miniature version of the shock tubes indeed produced high intensity shock waves as predicted by the shock wave theory. Apart from the shock tube actuators, fast acting solenoid valves which does not produce any shock were also tested, to compare the efficacy of both types of actuators. The later part of the work focuses on the actual application of these actuators as flow control devices. First, we delve into the acoustic suppression results which show the amount of tonal noise suppression achieved by using these actuators. For the M = 0.6 case the valves produced very good suppression up to 20 dB but the mass flow rate of these valves were about 26% of the main jet mass flow rate. In the M = 0.8 flows the valves produced negligible suppression. The multiple shock tube performed better than the single shock tube in both cases with a tonal noise suppression of up to 12 dB and 10 dB for M = 0.6 and M = 0.8 flows, respectively. The effect of the shock wave on the cavity tone was evident from the results and had a memory effect on the cavity tone suppression. Due to this the mass flux and the momentum coefficient for the shock tube actuators were considerably low. In order to better understand the mechanism through which the actuators suppress cavity tones, mean velocity measurements and phase averaged pressure measurements were carried out. Based on these results, it was observed that the lifting of the shear layer was the dominant mechanism behind steady and pulsed mass injection. In addition to this beamforming, used for locating the noise sources, was also used to study the cavity tones. Detailed discussion of the results are presented in this report.
M.S. in Mechanical and Aerospace Engineering, May 2011
Show less

Title: Motive power and distribution charges of a packing plant
Creator: Waldemar Sir, Walter
Date: 2009, 1918
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/motivepowerdistr00wald
Thesis (B.S.)--Armour Institute of Technology

Title: INVESTIGATION OF BI-IN-SN AND BI-IN-SN-GA AS PHASE CHANGE MATERIALS
Creator: Huynh, Hong Trang
Date: 2012-05-02, 2012-07
Description: Phase change energy storage is one of the most effective ways to store thermal energy. The difference between metallic phase change materials ...
Show morePhase change energy storage is one of the most effective ways to store thermal energy. The difference between metallic phase change materials (PCMs) and organic and inorganic PCMs is discussed. Bi-In-Sn and Bi-In-Sn-Ga alloys with near eutectic compositions were analyzed using DSC, X-Ray, EDS and metallography to establish the alloy properties. An attempt was made to package the alloy in metallic and non-metallic foams and various tests such as infiltration and cycling tests were conducted to test the feasibility of various containment materials. These PCM alloys were applied in a prototype cooling system of electronic devices for better heat dissipation than conventional heat sinks. Tests were conducted to measure the effectiveness of the alloys. Different designs were suggested for the containment of the alloy.
M.S. in Mechanical, Materials, and Aerospace Engineering, July 2012
Show less

Title: Computing transition and flow development in turbulent channel flows
Creator: Sallot, Thomas
Date: 2012-12-05, 2012-12
Description: A zero pressure gradient (ZPG) boundary layer in a wind-tunnel test section was computed using two-dimensional CFD simulations utilizing two...
Show moreA zero pressure gradient (ZPG) boundary layer in a wind-tunnel test section was computed using two-dimensional CFD simulations utilizing two RANS models, Spalart-Allmaras (SA) and k􀀀! (SST), and two di erent software suites; i.e., Fluent and STAR-CCM+. These computations have been compared and they revealed that the SST model yields better agreement with experimental data than the SA. They also demonstrate that STAR-CCM+ has very little sensitivity to small pressure gradients, and that is why its computation for the ZPG are not exactly matching the reference data (experiment and DNS). Further analysis of the two softwares leads to the conclusion that the transition is dealt with di erently. These di erent approaches can also contribute to the discrepancies observed in the results. The second part of this study is aimed at analyzing the SA model and proposing an approach to improve its results. Tests on the various options proposed in STAR-CCM+ led us to understand how crucial it is to know the e ect of each setup. In addition, several DNS pro les have been used as in ow conditions for the ZPG problem in order to show that this model can be signi cantly improved by using the appropriate in ow conditions past the transition of the boundary layer. Alternatively, incorporating a transition model into the SA computations based on an approach like the en model, or more advanced transition codes, can result in much better agreement with experiments and recent DNS results. The third part of this work is focused on one of the most computed ows in turbulence: the channel ow. The rst goal was to con rm that an implementation of transition similar to that in the ZPG case can be e ectively used for the channel. The second focus was to nd a criterion to establish the required fetch for the fully developed region in a channel. The criterion found here is based on the asymptotic trend of the centerline velocity and its result indicates a longer distance than the usual xi 100 to 150 full channel heights found in the literature, especially at low Reynolds numbers. Finally, this study reveals the three dimensionality of the channel which appears to be impossible to avoid even for extremely high aspect ratios. Using the RSM model, the results document how the channel ow contains secondary motions, sidewall boundary layers and streamwise vortices that exchange energy and momentum between the center and the side walls. Therefore, channel ows need to be calculated as a 3D problem in order to be modeled properly or to be representative of any physical laboratory experiment.
M.S. in Mechanical and Aerospace Engineering, December 2012
Show less

Title: DEVELOPMENT OF ACTIVE RESPONSE TECHNOLOGY FOR SAFETY APPLICATIONS IN POWER SAWS
Creator: Assaliyski, Marin I.
Date: 2014, 2014-05
Description: This thesis presents a study of kickback occurrences on table saws, as well as the development and evaluation of a system designed to mitigate...
Show moreThis thesis presents a study of kickback occurrences on table saws, as well as the development and evaluation of a system designed to mitigate health and property hazards due to kickbacks. A kickback is an unwanted situation during the cutting process of many powered circular saw tools, during which the operator of the tool loses control, potentially resulting in severe property and bodily harm. Multiple safety devises exist to prevent this type of situation from occurring; however, all of these devices are passive and often become a burden by decreasing e ciency, and are therefore often removed by the users. This thesis seeks to study the occurrence of kickbacks and to present an active electronic detection system that is able to aid in mitigation of potential damage to property or persons by developing responsive, robust, and practical methods of kickback detection. Implemented detection methods are presented and evaluated for performance. Concepts are also developed, presented, and discussed with the purpose of generating topics for future work. An experimental brake is used to evaluate the performance of the detection methods with an integrated system.
M.S. in Mechanical and Aerospace Engineering, May 2014
Show less

Title: ENERGY SAVINGS FOR UAV FLIGHT IN UNSTEADY GUSTING CONDITIONS THROUGH TRAJECTORY OPTIMIZATION
Creator: Grimaud, Lou
Date: 2014, 2014-07
Description: The purpose of this thesis is to show how micro unmanned aerial vehicles can extract energy from periodic wind gusts and how this energy...
Show moreThe purpose of this thesis is to show how micro unmanned aerial vehicles can extract energy from periodic wind gusts and how this energy extraction is a ected by the e ects of unsteady aerodynamics and the spatial structure of the gust component. The trajectory of a small UAV ying through wind gusts is simulated with a two degree of freedom model. The non-dimensional model is set to include vertical and horizontal gusts of varying amplitudes and durations. From this model an optimization routine is performed in order to obtain the minimum gust amplitude needed to obtain a neutral energy trajectory. With these results, it is shown that neutral energy ight is possible through gusts speeds of only 10 to 30% of the ying speed of the aircraft. Analysis of the results shows that the lift coe cient has to be changed very rapidly in order to perform these maneuvers in short duration gusts. Moreover high lift values are often required. To achieve this kind of rapid change in the lift and drag forces, fast variations of the angle of attack are needed. The high lift values also require high angles of attack that are likely to cause separation of the ow over the airfoil. These fast variations at high angle of attack are shown to cause unsteady non linear aerodynamic responses. Traditional CFD simulations are far too computationally expensive to be implemented into the optimization routine. To solve this issue a low order model based on a paper by Goman and Khrabrov [7] (GK) is developed and validated against experimental results. This model produces accurate predictions of the lift and drag coe cients for a wide range of angles of attack and for di erent type of pitch inputs. With this GK model the in uences of the unsteady aerodynamics on the energy extraction problem are highlighted. The main di erence with quasi-steady aerodynamics model was found to be for gusts at a reduced frequency (k = cf u ) higher than 0.07. Around these values the potential performance is improved by introducing the unsteady model. The trajectories obtained include more violent changes in angle of attack in order to take full advantage of the unsteady e ects.
M.S. in Mechanical, Materials, and Aerospace Engineering, July 2014
Show less

Title: DEVELOPMENT OF MULTI-NOZZLE MICRO-EXTRUDER FOR LAYERED MANUFACTURING OF MULTI-MATERIAL ENERGY STORAGE DEVICES
Creator: Mohamed Ayub, Shaik Mohamed Imran
Date: 2014, 2014-05
Description: Additive Manufacturing is critical in the development of high energy density storage devices for its flexibility to manufacture complex parts...
Show moreAdditive Manufacturing is critical in the development of high energy density storage devices for its flexibility to manufacture complex parts with different discrete compositions like cathodes, anodes and electrolytes. Such storage devices under sub- millimeter scale with micro-structured interdigitated layout could significantly improve its power and energy density. Over the past few years, scientific communities in Rapid Prototyping technology have been mainly focusing on various methods of Modeling and representing Multi-Material Object under single CAD data structure which would enable post processing and rapid prototyping of Multi-Material Object (MMO). This thesis will address the processes involved in the development of Multi-Material Micro Extrusion (M3E) device for manufacturing high density energy storage devices through discrete composition control in Solid Freeform Fabrication (SFF). The primary goal of the research is to develop a rectilinear motion platform with a multi-extrusion system and an open loop control interface to regulate the unreliable extrusion of slurries of different discrete composition. The dissertation will also address the software methodology to discretize 3D-CAD models to represent multiple material composition followed by slicing it into 2.5D layers, which will enable to create Computer Numeric Control (CNC) path program. The scope of this research is further extended to study and optimize various mechanical process inputs with respect to extrusion output parameters.
M.S. in Mechanical and Aerospace Engineering, May 2014
Show less

Title: RELATIVE RECEIVER AUTONOMOUS INTEGRITY MONITORING FOR FUTURE GNSS-BASED AIRCRAFT NAVIGATION
Creator: Gratton, Livio Rafael
Date: 2011-05-15, 2011-05
Description: The Global Positioning System (GPS) has enabled reliable, safe, and practical aircraft positioning for en-route and non-precision phases of...
Show moreThe Global Positioning System (GPS) has enabled reliable, safe, and practical aircraft positioning for en-route and non-precision phases of flight for more than a decade. Intense research is currently devoted to extending the use of Global Navigation Satellite Systems (GNSS), including GPS, to precision approach and landing operations. In this context, this work is focused on the development, analysis, and verification of the concept of Relative Receiver Autonomous Integrity Monitoring (RRAIM) and its potential applications to precision approach navigation. RRAIM fault detection algorithms are developed, and associated mathematical bounds on position error are derived. These are investigated as possible solutions to some current key challenges in precision approach navigation, discussed below. Augmentation systems serving large areas (like the Wide Area Augmentation System (WAAS) covering the North American continent) allow certain precision approach operations within the covered region. More and better satellites, with dual frequency capabilities, are expected to be in orbit in the mid-term future, which will potentially allow WAAS-like capabilities worldwide with a sparse ground station network. Two of the main challenges in achieving this goal are (1) ensuring that navigation fault detection functions are fast enough to alert worldwide users of hazardously misleading information, and (2) minimizing situations in which navigation is unavailable because the user‟s local satellite geometry is insufficient for safe position estimation. Local augmentation systems (to be implemented at individual airports, like the Local Area Augmentation System or LAAS) have the potential to allow precision approach and landing operations by providing precise corrections to user-satellite range measurements. An exception to these capabilities arises during ionospheric storms (caused by solar activity), when hazardous situations can exist with residual range errors several orders of magnitudes higher than nominal. Until dual frequency civil GPS signals are available, the ability to provide integrity during ionospheric storms, without excessive loss of availability, will be a major challenge. For all users, with or without augmentation, some situations cause short duration losses of satellites in view. Two examples are aircraft banking during turns and ionospheric scintillation. The loss of range signals can translate into gaps in good satellite geometry, and the resulting challenge is to ensure navigation continuity by bridging these gaps, while simultaneously maintaining high integrity. It is shown that the RRAIM methods developed in this research can be applied to mitigate each of these obstacles to safe and reliable precision aircraft navigation.
Ph.D. in Aerospace Engineering, May 2011
Show less

Title: SHORT AND ULTRASHORT-PULSED LASER-MATERIAL INTERACTIONS: MODELING AND COMPARISONS WITH EXPERIMENTS
Creator: Tao, Sha
Date: 2013, 2013-07
Description: Lasers have wide applications in numerous areas. Laser-based applications and technologies often involve certain types of laser-material...
Show moreLasers have wide applications in numerous areas. Laser-based applications and technologies often involve certain types of laser-material interactions, many of which have not been sufficiently understood. In this thesis, through the development of the corresponding physics-based models and the comparisons of modeling results with relevant experiments (when available), the laser-material interaction mechanisms during the following processes will be studied: i) laser ablation of semiconductors; ii) laser-material interactions inside microholes; and iii) laser-induced plasma evolution (more detailed conditions of the studied processes are given in the thesis). This research work is expected to improve the understanding of laser-material interaction mechanisms in the above investigated processes, which may provide information that is useful for the improvement of many related existing laser-based applications or technologies and for the development of novel ones.
PH.D in Mechanical and Aerospace Engineering, July 2013
Show less

repository.iit

Search the repository

Pages

Pages

Enabled Filters

Refine Results

Type

Date

Academic status of creator

Subject

Creator

Rights